You realize a supercharger kit installed and tuned is 10k plus .... so he won’t be ahead at all
Guess it depends on what options you add to the kit.
My total bill for the SC package with tune, oil gear and boost gauge is under $7,400.
Install for gear is $900
Install for SC + plugs, if I go that route, is $1,500.
$1,300 of that bill is oil pump gear+install, which most opt out of.
That being said if the OP wants an 18, then do it. His truck with his miles, down here in FL goes on the lots starting in the high 40's.
If he got offered 46k, then do that deal before the # drops.
MPG wise though, is 2-3 MPG that big of a difference for Daily driving or not?
I mean, you don't buy a truck with 35"s and then worry about fuel efficiency.